1. Field of the Invention
The present invention relates to the R1 resistance gene from potato. It further relates to methods and materials employing the gene, and processes for identifying or producing other related genes. It also relates generally to methods for identifying plant protective agents which are capable of inducing the R1 gene or the activity of its encoded protein. Furthermore, the present invention relates to transgenic plants which became resistant to Late Blight because of the expression of an R1 transgene.
2. Description of Related Art
Several documents are cited throughout the text of this specification by name. Full bibliographic citations may be found at the end of the specification immediately preceding the sequence listing or claims. Each of the documents cited herein (including any manufacturer's specifications, instructions, etc.) are hereby incorporated herein by reference; however, there is no admission that any document cited is indeed prior art as to the present invention.
Late blight is worldwide the most destructive disease for potato cultivation causing billion-dollar losses every year (Kamoun et al. 1999). The causal pathogen is Phytophthora infestans, an oomycetous fungus infecting also tomatoes (Judelson 1997). Complete destruction of the potato crop by late blight caused the “Irish potato famine” in the middle of the 19th century (Salaman 1985) and initiated the search for resistant plants. Single genes for resistance to late blight (R genes) were discovered nearly 100 years ago in S. demissum, a wild potato species indigenous to Mexico. Introgression into potato cultivars of R genes conferring race specific resistance provided, however, only transient resistance to late blight, as new races rapidly overcame the R gene mediated resistance (Wastie 1991, Fry and Goodwin 1997). Quantitative or field resistance to late blight has also been identified in wild potato species (Ross 1986). This resistance is more durable than the one mediated by R genes, but difficult to move into cultivated varieties by crossing and phenotypic selection. Late blight is still mostly controlled by the frequent application of fungicides which loose efficiency by selection of fungicide resistant isolates.
Several R genes have been mapped to potato chromosomes using DNA markers (Leonards-Schippers et al. 1992, El-Kharbotly et al. 1994, 1996, Li et al. 1998, Ewing et al. 2000, Naess et al. 2000). R1 is located on chromosome V (Leonards-Schippers et. al., 1992) in a region where single genes for resistance to Potato virus X have also been mapped (Ritter et al. 1991, De Jong 1997). The same region contains major quantitative trait loci (QTL) for resistance to the parasitic root cyst nematode Globodera pallida (Kreike et al. 1994, Rouppe van der Voort et al. 1997, 2000) and late blight (Leonards-Schippers et. al. 1994, Oberhagemann et al. 1999, Collins 1999). The presence of a hot spot of resistance genes suggests their evolution from common ancestors by local gene duplication followed by functional diversification (Leonards-Schippers et al. 1994, Leister et al. 1996, Oberhagemann et al. 1999, Gebhardt and Valkonen 2001). If this is the case, the molecular cloning of the R1 gene should open the possibility to study at the molecular cloning factors mapping to the region and participating to the control of qualitative and quantitative resistance to various pathogens.
Thus, the technical problem underlying the present invention was to comply with the need for plant pathogen resistance genes and their regulatory sequences.
The solution to the technical problem is achieved by providing the embodiments characterized if the claims and described further below.